Data sources
Astronomer computes the sky on your phone, and reads two services for what cannot be computed: the space weather of the NOAA and the weather forecasts of MET Norway.
Read by our server
| Source | Data | Licence | Read |
|---|---|---|---|
| NOAA Space Weather Prediction Center National Oceanic and Atmospheric Administration (United States) | The forecast of the auroral oval (OVATION), the planetary K-index and its 3-day forecast, the solar wind | Public domain (work of the U.S. Government) | every 10 min |
| MET Norway Norwegian Meteorological Institute | Clouds by layer, fog, humidity, dew point, temperature, wind and precipitation, hour by hour | CC BY 4.0 | at each forecast, kept until it expires |
In the app
The app carries its own catalogues and computes the positions itself. The share-alike catalogues are credited here, and the files Astronomer derives from them are published under the same licence.
- HYG Database (David Nash, astronexus.com) · CC BY-SA 4.0
- Stellarium, western sky culture · CC BY-SA
- OpenNGC (Mattia Verga) · CC BY-SA 4.0
- International Astronomical Union · facts, freely usable
- Astronomy Engine (Don Cross) · MIT
- Natural Earth · Public domain
How the sky is computed
The positions of the Sun, the Moon and the planets come from series of the VSOP87 and ELP theories, those of the stars from their catalogue positions brought to the date (precession, proper motion), then turned into your horizon’s coordinates with the time, your position and the refraction of the air. The calendar of events is computed once a year by our server with Astronomy Engine.
How accurate is it?
About an arcminute for the Sun, the Moon and the planets, and the minute for the times of rising and setting, for a flat horizon at sea level. Forecasts are forecasts: the clouds and the aurora can surprise the best models. The sky map’s direction depends on the compass of your phone.
Looking at the Sun
Never look at the Sun directly, nor through binoculars, a telescope or a camera, without a certified solar filter (ISO 12312-2): it burns the eye in an instant, without pain. The camera finder shows the Sun on the screen only. During a solar eclipse, use eclipse glasses or a filtered instrument.